Agencies Which Improve the Soil 3 



freezing temperature in pulverizing his soil. This facili- 

 tates the beneficial influence of the air by allowing it 

 free access to the particles of soil, which are thus acted 

 upon by the constituents oxygen and carbonic acid. 

 This, in turn, makes the soil a comfortable home for the 

 beneficial species of bacteria, the nitrifiers. 



How fortunate are we in having the services of these 

 powerful, though silent and unseen, laborers at our bid- 

 ding, especially when we consider that they require only 

 such intelligent manipulation of the soil as will render 

 their invaluable, freely rendered services practicable, 



GENERAL CLASSIFICATION OF SOILS 



There is a perpetual movement of soil, together with 

 portions of the decomposing organic matter upon its 

 surface, from higher to lower elevations. Where there is 

 small variation in the surface elevations of the country, 

 the larger part of the disintegrated material remains 

 where it is formed. These are termed by geologists sed- 

 entary soils, or soils in place. Their mineral constituents 

 are proximately known by the indications of the chemical 

 analysis of the parent rock. 



That considerable movement of such soils, and espe- 

 cially of their organic constituents, has taken place, is 

 shown by the greater productiveness of slight depressions 

 compared with that of the more elevated portions of the 

 surface. 



Transported Soils are those which have been so far 

 removed from the place of their birth that no reliable in- 

 dication of their source remains. These are divided into: 



